An electrochemical fuel cell is a device that converts fuel and an oxidant to electricity, a reaction product, and heat. For example, fuel cells may be adapted to convert hydrogen and oxygen into water, electricity, and heat. In such fuel cells, the hydrogen is the fuel, the oxygen is the oxidant, and the water is the reaction product.
A fuel cell stack typically includes two or more fuel cells, including groups of fuel cells, coupled together as a unit. A fuel cell stack may be incorporated into a fuel cell system. A fuel cell system also typically includes a fuel source, such as a supply of fuel and/or a fuel processor, which produces hydrogen gas or another suitable proton source for the fuel cell stack from one or more feedstocks. An example of a fuel processor is a steam reformer, which produces hydrogen gas from water and a carbon-containing feedstock. The system may also include a battery bank, which stores produced electrical power, and an air source, which delivers oxygen to the fuel cell. There is a need to control fuel cell stacks and other fuel cell system components to regulate the operation of the system, such as to prevent damage to the system and/or to operate the system efficiently in response to changing operating conditions.